Mongoose Schema Error: “Cast to string failed for value” when pushing object to empty array

Question

I have a strange problem and cannot figure out what the problem is. The Error-message doesn\'t help.

I\'m sending an "alarm" to the server and want to save

Answer 1

Mongoose interprets the object in the Schema with key 'type' in your schema as type definition for that object.

deviceId: {
  type : String,
  index : {
    unique : true,
    dropDups : true
    }
}

So for this schema mongoose interprets deviceId as a String instead of Object and does not care about all other keys inside deviceId.

SOLUTION:

Add this option object to schema declaration { typeKey: '$type' }

var deviceSchema = new Schema(
{
   deviceId: {
        type : String,
        index : {
            unique : true,
            dropDups : true
        }
    },
    alarms : [ {
        timestamp : Number,
        dateTime : String, //yyyymmddhhss
        difference : Number,
        actionTaken : String, //"send sms"
    } ]
},
{ typeKey: '$type' }
);

By adding this we are asking mongoose to use $type for interpreting the type of a key instead of the default keyword type

Mongoose Docs reference: https://mongoosejs.com/docs/guide.html#typeKey